At present, an electromagnetic resonance circuit with a single insulated gate bipolar transistor (IGBT for short) generally adopts a parallel resonance mode, and when resonance parameters for realizing a high power operation of an electromagnetic oven are used, there may be following problems if the electromagnetic oven continuously operates at a range of low power.
(1) The IGBT is turned on with a leading voltage, and a high instant current peak value may be caused at the moment of the IGBT is turned on, which is likely to exceed a specification limit of the current peak value of the IGBT, thus damaging the IGBT.
(2) The IGBT may emit heat greatly, and it is required to strengthen heat dissipation (such as to enlarge cooling fins, to improve the rotate speed of the fan) of the IGBT, so as to satisfy a temperature rise demand of the IGBT.
(3) If the low power is realized under a duty ratio heating mode, i.e. if a discontinuous heating mode is used, there is a hard turn-on phenomenon when the IGBT turns on in a next period because of the existence of a filter capacitor, which is likely to damage the IGBT.